How to Conduct a Christmas Bird Count

Following the 100th CBC, the official count period was expanded and fixed at the dates of December 14 through January 5 for all future seasons. Individual Count Compilers are free to choose a day within that period. This will help for planning in the years ahead. All counts must run within these dates.

The Compiler's Manual details specifics of conducting a count, including scouting, contacting participants, how to record weather and effort information, and the participant fee policy. In addition, we have provided one printable handout—a description of CBC effort—for compilers to hand out to participants in the field.

For the first century of the Christmas Bird Count, the official count period was a floating period of time, either 17 or 18 days long, that wobbled about on the calendar from mid-December through early January. There was a great amount of confusion each season as to when the count period began and ended. And one of the cardinal rules of the CBC is that we cannot accept CBCs that are conducted outside the count period, as they are not statistically comparable with all the rest of the counts.

Beginning with the 101st CBC, and after an analysis of the date ranges within the cumulative CBC database, we expanded and fixed the dates of the official CBC period from December 14th (the earliest date that any count was included in the entire 100-year CBC database) to January 5th (the latest date of any count in the database). This expanded the CBC period from 17 days to 23 each season, and also conveyed the huge advantage of always being the same date range, much easier for compilers's planning purposes from year to year. Most CBC compilers plan on conducting their counts on a given day (perhaps the first Saturday of the count period, or the Saturday after New Years), usually on a weekend, during the count period.

For a myriad of reasons we cannot ever expand the CBC period beyond the current date range of December 14th through January 5th and CBC counts cannot take place outside of these dates.

The CBC count period in fact is still a time when birds on a population level are actively moving southward.

It's entirely true that neotropical migrant species, those that leave the US and Canada in the fall and go to Latin America for the winter, for the most part (except for those exciting rarities and stragglers that entice CBC observers out each season) are down south where they are "supposed" to be.

However, the avifauna that winters within the North American region (at least the United States and Canada) is still very much in movement through early January. Many factors affect where and how far south some species linger, especially water-dependent species like waterfowl and rails, or bare ground dependent species like Snow Buntings, Horned Larks, and many other sparrow relatives. Even frugivores and insect eaters like American Robins, Hermit Thrushes, and Eastern Bluebirds are affected seasonally and can vary significantly from year to year where their center of abundance is during the CBC period. A cold, snowy fall and early winter will force these species farther southward; a mild fall and early winter will allow them to linger much farther northward, even into southern Canada. Hard early winters are greatly to the benefit (both numbers of birds and species diversity wise) of counts in the south; mild seasons hugely benefit counts in the north. Both weather-wise and bird-wise December 14th through January 5th is a time of great flux, with amazing annual geographical variation in many species. The days and weeks before and after the count period as it stands now are even more drastically affected by these types of species's annual variation.

The Christmas Bird Count has evolved to become a hugely important pool of data for researchers studying the ongoing status and ranges of bird populations across the Americas. The only other similar yardstick is the Breeding Bird Survey (BBS), run during June in the breeding season. The co-analyses of CBC and BBS have become the combined yardstick by which ornithologists and conservation biologists assess how bird populations are doing--and where they are occurring--across the Americas. It is Audubon's mandate and duty to keep the CBC database as meaningful and statistically significant as possible. It was a many-decade struggle for the scientific community to embrace the CBC and other community science databases as statistically meaningful for scientific study; we must not do anything to jeopardize that trust.

During the fall of 2003 we undertook an independent Scientific Peer Review of the Christmas Bird Count, similar to that which was done for the Breeding Bird Survey some years earlier. The full recommendations of the peer review panel were published in the 104th CBC issue of American Birds and are available online here.

One of the over-arching, imperative recommendations of the peer review panel was that we never again expand the CBC period. If we were to do so that would greatly alter the meaningfulness of trend data in the CBC database, effectively ending the run of CBCs and their associated database that has been done for over a century, and begin an entirely new study. One of the largest databases in the study of birds would be terminated.

The CBC period has been expanded as far as can possibly be done. To maintain the integrity of the database, to maintain the value of the CBC to conservation science, and to ensure the value of the efforts of the tens of thousands of observers each season who volunteer their time to the Christmas Bird Count, we cannot expand the Official Count Period beyond the dates where they currently are set.

Count week is defined as from 3 days before to 3 days after your official count day. If your official count day is December 14, then your Count Week extends from Dec 11 to Dec 17 (and can therefore extend outside of the official count period of Dec 14-Jan 5).

Count week (cw) birds serve as a place holder for that species on your checklist in a given season. They are not at all a part of your official census data for that season's day.

Birds seen during the 3 days before or after your count day but NOT on your official count day are recorded on your checklist as "cw". No other information about count week birds are recorded in the CBC database. Numbers observed of count week birds are not recorded nor added to other numbers, and the date of when a count week bird was seen, is not recorded.

Count week listings do not count toward your species total or toward your number of individuals on count day.

It is up to the compiler as to whether time should be spent in the field looking for count week birds. It is not a requirement of the CBC to go out and observe birds during count week, but scouting time ahead of the count day, if it occurs during count week, can be an opportunity to notice these other birds.

Numbers for any species seen on count day are the ones to be included. Even if larger numbers of a given species were found during count week than on count day, only the tally from the official census day should be entered on your checklist.

Example 1: If you reported 11 Great Blue Herons on your official count day, you cannot include Great Blue Heron as a count week bird, but you should enter "11" as the number for Great Blue Heron on your checklist. But if you did NOT see Great Blue Heron on your official count day, and did see it one day before your official count day, then you would record a "cw" in the number box of your CBC checklist for Great Blue Heron.

Example 2: If you found 11 Great Blue Herons during the count week but only 4 on count day, the number to include in your official checklist tally is 4--the number seen on count day.

The printable version of the Rare Bird Form can be viewed and printed using Adobe Acrobat Reader. A editable, Word version of the form is also available. The completed rare bird form is to be sent directly to the Regional Editor for your region not to Audubon. Click link for mail and email addresses.

Because the CBC is monitoring birds in the non-breeding season (and most species are not singing, at least in North America) the use of playback and attractant noises have always been permitted on the CBC, where allowed by law. With the proliferation of iPods and other hand-held devices that can readily play bird vocalizations and elicit responses from otherwise hidden birds, this use is reported to be on the rise.

If prudent use of audio broadcast has been used routinely on a CBC, those methods should be continued to maintain consistent counting data over time.

The use of playback on a CBC should be very judicious, and never done in a fashion that could affect the behavior of target species in any significant way.

We've prepared a Powerpoint presentation that compilers and chapters can use to give an orientation to the Christmas Bird Count to any general audience. You'll find links to the presentation, the presenter's guide, which includes a script for the presentation, and tip sheet on giving presentations. To view the presentation on your computer or to present it in front of an audience, you will need to download the Microsoft Powerpoint Viewer

This printable handout is for compilers or sector leaders to give to participants on the day of the count. This handout covers the basics of what participants will be doing on count day and what data they need to record as they go about counting birds. The printable form is set to print two handouts per page.

Printable instructions on how to work with the CBC data entry system and complete your data entry are available above. You will need Adobe Acrobat Reader (free) installed on your computer to be able to view and print these instructions.

It is still important to keep the names on your participant list accurate for each season, as well as the numbers in the effort section of the online database. In this way we can make sure that folks' names are properly acknowledged for all the counts on which they participate each season.

While we will no longer be doing a physical mailing of American Birds to participants, it's becoming increasingly important that we have participants' email addresses as well as their names included in the database each season. This is because we hope to be able to be directly in touch with CBC participants as features and updates are released on the Christmas Bird Count website, or for important announcements about the CBC. Having the emails for participants will streamline things for Audubon Science as well as for compilers, and will enable us to be in touch with participants in a more timely manner. You should also now include this same information for all of your feeder watchers. Their information had not been required prior to the 113th CBC.

Questions About CBC Circles, or Proposing a New CBC Circle

To RESTART an existing, inactive CBC circle, please email cbcadmin@audubon.org with details on the circle name, code (if you have it) or other details to identify the circle. We will research the circle in the database and confirm that it can be restarted. The same guidelines apply as those for starting a new circle with regard to coverage:

There must be an assurance that at least 10 participants will be available every year to do the count to ensure continued good coverage.

Want to start a new count in your area? There are now over 2500 CBCs in the United States, Canada, Hawaii, the Pacific Islands, the Caribbean, Central and South America, and the more the merrier! In order for you to start a new Christmas Bird Count in your area you will need to submit a New Count Application through the link above or below with the following information between September 1 and December 1:

The permanent name of your new count, along with the description and exact latitude and longitude (in decimal degrees only) of the center point of your 15-mile diameter circle. The lat/long information in decimal degree format is critical to get your count set up in the CBC database.

An assurance that at least 10 participants will be available every year to do the count, along with a description of the experience level of the party leaders, to ensure continued good coverage.

Name, phone number and email of compiler. Please note that an email address is mandatory to enter data.

Optionally, a general geographic and habitat descriptions of the area, including percentages of habitat types, an indication of the vegetation in each habitat, and why the area is important.

While we look forward to receiving the information on your new CBC by December 1, we recommend that if you haven’t already you run a trial count for the first season before sending us the application. This helps ensure that your proposed circle is one you and your participants will be happy with for the future. In running a trial count, unanticipated logistical problems may be discovered, and you can make sure your circle includes the best possible combination of local habitats, as well as ensure you have enough participation to adequately cover the area.

When we receive your application, we will review it and get back to you as soon as possible if there is any problem. If everything is in order, you will be contacted to confirm you can go ahead with your new count.

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